Three dimensional printing system with improved optical path

ABSTRACT

A three dimensional printing system includes a support plate, a resin vessel, and one or more mechanical features. The support plate includes a ridge surrounding a first central opening. The resin vessel includes a vessel body defining an inner edge surrounding a second central opening and a transparent sheet that closes the central opening to define a lower bound for a body of resin to be contained within the resin vessel. The one or more mechanical features are configured to align and secure the resin vessel relative to the support plate whereby the ridge engages a lower surface of the transparent sheet to tension the transparent sheet and the ridge is laterally recessed inwardly relative to the inner edge of the vessel body.

FIELD OF THE INVENTION

The present disclosure concerns an apparatus and method for fabricationof solid three dimensional (3D) articles of manufacture from radiationcurable (photocurable) resins. More particularly, the present inventionimproves the fabrication accuracy of a three dimensional (3D) article ofmanufacture by reducing an optical path variation.

BACKGROUND

Three dimensional (3D) printers are in rapidly increasing use. One classof 3D printers includes stereolithography printers having a generalprinciple of operation including the selective curing and hardening ofradiation curable (photocurable) liquid resins. A typicalstereolithography system includes a resin vessel holding thephotocurable resin, a movement mechanism coupled to a support surface,and a controllable light engine. The stereolithography system forms athree dimensional (3D) article of manufacture by selectively curinglayers of the photocurable resin. Each selectively cured layer is formedat a “build plane” within the resin.

One challenge with stereolithography systems is an optical pathvariation across the build plane that arises due to deformation and wearof certain portions of the resin vessel. What is needed is a way ofassuring that the optical path remains dimensionally accurate even afterrepeated fabrication of three dimensional (3D) articles of manufacture.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is an isometric drawing depicting an exemplary three dimensionalprinting system.

FIG. 1B is a side view of an exemplary three dimensional printingsystem.

FIG. 1C is a rear view of an exemplary three dimensional printingsystem.

FIG. 2A is a schematic block diagram of an exemplary three dimensionalprinting system.

FIG. 2B is an illustration depicting a “build plane” which represents athin slab of resin being selectively cured by a light engine.

FIG. 3A is a top view of an exemplary resin vessel.

FIG. 3B is a side view of an exemplary resin vessel.

FIG. 3C is an isometric view of a lower side of an exemplary resinvessel.

FIG. 3D is a bottom view of an exemplary resin vessel.

FIG. 4 is a top view of an exemplary support plate.

FIG. 5A is a top view of an exemplary support fixture.

FIG. 5B is a side view of an exemplary support fixture.

FIG. 5C is a diagram illustrating an “inflow distance” of resin flowingthrough openings in the support fixture.

FIG. 6 is a flowchart depicting an exemplary method of manufacturing athree dimensional article of manufacture.

FIG. 7A is an isometric drawing depicting loading a resin vessel onto asupport plate with an interface mechanism in a non-operating state.

FIG. 7B is an isometric drawing depicting loading a resin vessel onto asupport plate with an interface mechanism in an operating state.

FIG. 7C is an isometric drawing depicting a fluid spill containmentvessel about to be loaded onto a lower side of a support plate.

FIG. 7D is an isometric drawing depicting a fluid spill containmentvessel loaded onto a lower side of a support plate.

FIG. 8A is a simplified cross sectional schematic illustration oftensioning of a transparent sheet.

FIG. 8B is a simplified diagram of force exerted on the transparentsheet of FIG. 8A.

FIG. 8C is a simplified cross sectional schematic illustration of analternative method of tensioning a transparent sheet.

FIG. 9 is an isometric drawing depicting loading a support fixture ontoa receiving arm.

FIG. 10 is a top view of a portion of an exemplary three dimensionalprinting system with a resin vessel and support fixture installed.

SUMMARY

In a first aspect of the disclosure, a three dimensional printing systemincludes a support plate, a resin vessel, and one or more mechanicalfeatures. The support plate includes a ridge surrounding a first centralopening. The resin vessel includes a vessel body defining an inner edgesurrounding a second central opening and a transparent sheet that closesthe central opening to define a lower bound for a body of resin to becontained within the resin vessel. The one or more mechanical featuresare configured to align and secure the resin vessel relative to thesupport plate whereby the ridge engages a lower surface of thetransparent sheet to tension the transparent sheet and whereby the ridgeis laterally recessed inwardly relative to the inner edge of the vesselbody.

In one implementation the ridge has an inwardly facing surface thatbounds the first central opening.

In another implementation the support surface has an upper surfaceincluding a recess for receiving a lower portion of the resin vessel.The recess is bounded by an inwardly facing wall that functions as oneof the one or more mechanical features to laterally align the resinvessel relative to the support plate by engaging an outer peripheraledge of the resin vessel.

In yet another implementation the vessel body includes a pair of latchfeatures and the one or more mechanical features includes an interfacemechanism coupled to a pair of latches configured to engage the pair oflatch features to vertically secure the resin vessel relative to thesupport plate. The latches exert a downward force upon the latchfeatures. The support plate has an upper surface. The engagement of theridge and the transparent sheet prevent the vessel body from bottomingout on the upper surface of the support plate whereby the downward forceof the latches on the latch features increases the tension in thetransparent sheet. The three dimensional printing system also includes acontroller coupled to the interface mechanism. The controllerprogrammably controls the downward force of the latches on the latchfeatures whereby the tension in the transparent sheet is programmablycontrollable.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A-C are views of an exemplary three dimensional (3D) printingsystem 2. FIG. 1A is an isometric view, FIG. 1B is a side view, and FIG.1C is a rear view. In describing printing system 2 axes X, Y, and Z areused to illustrate positions, directions, and motions. Axes X, Y, and Zare mutually orthogonal. Axes X and Y are “lateral” or “horizontal”axes. Axis Z is a “vertical” axis. Axis Z is typically aligned or nearlyaligned with a gravitational reference. In describing directions thefollowing conventions will be used: +Y is to the “right” and −Y is tothe “left.” +Z is generally upward and −Z is generally downward.

Three dimensional printing system 2 includes a vertical support 4 havinga front side 6 and a back side 8. Vertical support 4 generally providesa “vertical backbone” from which other components of three dimensionalprinting system 2 are mounted.

A support plate 10 is mounted to the vertical support 4. Support plate10 has a proximal end 12 that is proximate to the front side 6 ofvertical support 4. Support plate 10 extends from proximal end 12 todistal end 14 along the lateral axis X. Support plate 10 has an innersurface 16 facing inwardly and defining a central opening 18.

A resin vessel 20 is supported by the support plate 10. The resin vessel20 has a rear portion 22 that is proximate to the proximal end 12 of thesupport plate 10. The resin vessel 20 has a front portion 24 that isproximate to the distal end 14 of the support plate 10. Resin vessel 20has an inner edge 26 that surrounds a central opening 28. The centralopenings 18 and 28 are laterally aligned with respect to each other toenable an optical path for vertically projected pixelated light. Centralopening 28 is laterally contained within central opening 18.

A resin fluid outlet 30 is positioned over the rear portion 22 of resinvessel 20. A fluid level sensor 32 is positioned over the rear portion22 of the resin vessel 20. The resin fluid outlet 30 and fluid levelsensor 32 are separated from each other along the lateral axis Y.

A fluid spill containment vessel 34 is releasably mounted to a lowerside 36 of the support plate 10. Fluid spill containment vessel 34 isfor capturing any resin spills resulting from damage to or overfillingof the resin vessel 20. The fluid spill containment vessel 34 includes awindow (to be discussed below). The window is laterally aligned with thecentral openings 18 and 28 to enable the aforementioned optical path forvertically projected pixelated light.

Mounted to the rear side 8 of vertical support 4 is a vertical track 38.A carriage 40 is mounted in sliding engagement with the vertical track38. A motorized lead screw 42 is configured to drive the carriage 40along vertical axis Z. The lead screw 42 is coupled to motor system 44which rotates the lead screw 42 to drive the carriage 40 verticallyalong the vertical track 38. A pair of fixture receiving arms 46 extendfrom the carriage 40 along the lateral axis X. Supported between thereceiving arms 46 is a support fixture 48.

A light engine 50 is mounted to the vertical support 4 via a supportbracket 52. Support bracket 52 extends away from the front side 6 ofvertical support 4 along lateral axis X. Pixelated light from lightengine 50 is projected vertically upwardly. The pixelated light passesthrough the fluid spill containment vessel 34, the support plate 10, andthe vessel 20 to a build plane within the resin vessel 20.

FIG. 2A is a block diagram schematic of the three dimensional printingsystem 2 including some mechanical features and a simplified electricalblock diagram. The resin vessel 20 is shown containing resin 54. Resinvessel 20 includes a transparent sheet 55 which defines a lower boundfor the resin 54 in vessel 20. The resin is being supplied from resinsupply 56 and along a resin supply path 58 to the resin fluid outlet 30.An interface mechanism 60 is configured to controllably latch the resinvessel 20 to the support plate 10 and to position the resin fluid outlet30 and the fluid level sensor 32 over the resin vessel 20.

The light engine 50 includes a light source 62 and a spatial lightmodulator 64. The light engine 50 projects pixelated light 66 up to a“build plane” 68 which is coincident with or proximate to a lower face70 of a three dimensional article of manufacture 72 being fabricated.Build plane 68 is depicted in FIG. 2B as a two dimensional array ofpixels 74. Each pixel 74 corresponds to a pixel element of the spatiallight modulator 64.

Build plane 68 defines a lateral addressable extent of the light engine50 within the resin vessel 20. The build plane 68 is actually a verythin slab or “slice” of resin with lateral dimensions in X and Y and asmall vertical thickness. This slab of resin is selectively cured basedupon a “slice” of data that is processed and sent to the spatial lightmodulator 64. The build plane 68 slab does not touch the transparentsheet 55 because an oxygen, chemical, or other inhibitor is utilized toblock polymerization on an upper surface of transparent sheet 55. Eachtime a portion of the build plane 68 slab is selectively cured, itprovides another accretive layer onto the lower face 70 of the threedimensional article of manufacture 72.

The thickness of resin between the lower face 70 and the transparentsheet 55 is important because it provides an optical path for thepixelated light 66. The weight of the resin 54 and other factors cancause the transparent sheet 55 to bulge between a center 76 and edges 78of build plane 68. Such a bulge will result in variable curing anddimensional variations as a function of a distance from the center 76.To reduce this factor, a unique tensioning mechanism is provided tomaintain flatness of the transparent sheet 55.

A controller 80 is controllably coupled to fluid level detector 32,motor system 44, light engine 50, resin supply 56, and interfacemechanism 60. Controller 80 includes a processor (not shown) coupled toan information storage device (not shown). The information storagedevice includes a non-transient or non-volatile storage device thatstores software instructions that, when executed by the controller 80,operate (and/or receive information from) fluid level detector 32, motorsystem 44, light engine 50, resin supply 56, interface mechanism 60, andother portions of three dimensional printing system 2. The controller 80can be located on one circuit board or distributed among multiplecircuit boards throughout the three dimensional printing system 2.

FIGS. 3A-D depict views of the resin vessel 20. FIG. 3A is a top view,

FIG. 3B is a side view, FIG. 3C is an isometric view, and FIG. 3D is abottom view of resin vessel 20. The construction of resin vessel 20includes resin vessel body 82, transparent sheet 55, and retainer 84that clamps the transparent sheet 55 to the resin vessel body 82.

The resin vessel body 82 has an outer peripheral edge 86 and inner edge26. Inner edge 26 defines the central opening 28 that is closed on alower side by the transparent film 55. Resin vessel body 82 includes asloped surface 88 surrounded by a peripheral wall 90 partly defining theouter peripheral edge 86. Peripheral wall 90 helps to contain the resin54 contained by the resin vessel 20. The sloped surface 88 allows resinto drain toward the central opening 28.

Resin vessel body 82 has a pair of opposing latch features 92 that arein opposing locations with respect to the lateral axis Y. Formed intothe sloped surface 88 of the vessel body 82 is a channel 96 forreceiving resin 54 from the resin fluid outlet 30.

FIG. 4 is a top view depicting the support plate 10. Support plate 10includes an upper surface 98 including a recessed surface 100 bounded byan inwardly facing wall 102. When the resin vessel 20 is loaded onto theupper surface 98 of support plate 10, a lower portion of resin vessel 20is partially received into a recess 101 defined between the inwardlyfacing wall 102 and a raised ridge 104 that rises above the recessedsurface 100. The resin vessel 20 is aligned to the support plate 10 byengagement between the outer peripheral edge 86 and the inwardly facingwall 102.

Extending above the recessed surface 100 is raised ridge 104. When theresin vessel 20 is loaded onto the support plate 10, the raised ridge104 engages a lower surface of the transparent sheet 55, therebylaterally tensioning the transparent sheet 55. The engagement betweenthe peripheral edge 86 and the inwardly facing wall 102 aligns theraised ridge 104 relative to the inner edge 26 of central opening 28 ofresin vessel 20. Aligned, the raised ridge 104 is disposed at asubstantially constant distance from the inner edge 26. Simultaneouslythe central opening 28 of the resin vessel is aligned relative to thecentral opening 18 of the support plate 10. In the illustratedembodiment the raised ridge 104 defines at least part of the inwardlyfacing surface or edge 16 that bounds and defines the central opening18.

FIGS. 5A and 5B depict support fixture 48. FIG. 5A is a top view andFIG. 5B is a side view. Support fixture 48 includes an upper portion108, a lower planar portion 110, and a side wall 112 coupling the upperportion 108 to the lower planar portion 110.

The upper portion 108 includes portions 108X that extend along thelateral X axis and portions 108Y that extend along the lateral Y axis.The portions 108Y are for supporting the support fixture 48 between thereceiving arms 46. Each 108Y portion includes a datum feature 114 forreceiving and aligning to pins that extend upwardly from the receivingarms 46. The portions 108Y are also made of a magnetic material that isheld down by magnets embedded in receiving arms 46. In an illustrativeembodiment the entire support fixture 48 is formed from a magneticmaterial. When the support fixture 48 is being raised, the receivingarms 46 provide support in an upper direction because the receiving arms46 press upwardly on the portions 108Y. When the support fixture islowered whereby lower planar portion 110 is passing into resin 54, themagnetic interaction between the upper portion 108 and the receivingarms 46 provides a downward force that secures the support fixture 48 tothe receiving arms 46.

The lower planar portion 110 has a lower surface 116 upon which thethree dimensional article of manufacture 72 is formed. Formed into thelower planar portion 110 is a dense array of small openings 118. Aprimary purpose of the small openings 118 is to reduce a fluid drag justbefore and at the start of forming the three dimensional article ofmanufacture 72. Before forming the three dimensional article ofmanufacture 72, the lower surface 116 is moved through the resin 54 andvery close to the transparent sheet 55. As the lower surface 116approaches the transparent sheet 55, resin is displaced and must flowlaterally from between the lower surface 116 and the transparent sheet55. Without such openings 118 the force exerted on the transparent sheet55 can be large enough to bulge or even damage the transparent sheet 55.

The openings 118 allow the resin 54 to escape vertically through thelower planar portion 110 of the support fixture 48. But there is still avertical force being exerted upon the transparent sheet 55. Thisvertical force varies positively with an “inflow distance” D. FIG. 5Cillustrates the inflow distance D between three small openings 118. Theinflow distance D is a geometric parameter that varies monotonicallywith a vertical force that is indirectly exerted between the lowersurface 116 and the transparent sheet 55 by the thin layer of resin 54therebetween.

The inflow distance 120 is geometrically defined as the distance thatresin must flow out of an opening 118 between the transparent sheet 55and the lower surface 116 before the entire lower surface 116 is coveredwith resin. This occurs when the dashed circles representing a “resinfront” flowing out of the circles close all uncovered gaps. Thistherefore occurs when the resin fronts intersect at a midpoint betweenthe arrangement of the three openings 118.

Defining some terms: S=the center to center distance between theopenings along Y. R=opening radius. D=the inflow distance between anedge of the opening and the midpoint between the openings. Usinggeometry, the result is that D=S/√3−R for this arrangement of openings.

For a particular example, the center to center distance S is 4.5millimeters. The opening radius R is 1.5 millimeters. Then the inflowdistance D is about 1.1 millimeters (rounding to the first significantfigure).

Preferably the dense array of small openings 118 cover the entire areaof the build plane 68 in order to minimize a vertical force exerted onthe transparent sheet 55. In one embodiment the dense array of smallopenings 118 includes at least 100 small openings 118. In anotherembodiment the dense array of small openings 118 includes at least 200small openings 118.

In some embodiments the inflow distance is less than 3 millimeters. Inother embodiments the inflow distance is less than 2 millimeters. In yetother embodiments the inflow distance is less than 1.5 millimeters.

The small openings 118 are the primary feature in reducing fluid dragand force on the transparent sheet 55 just before and at the beginningof forming the three dimensional article of manufacture 72 (and/or whenlower surface 116 is moving vertically through resin proximate to theupper surface of the transparent sheet 55). As the three dimensionalarticle of manufacture 72 is being formed, the distance between thelower surface 116 and the transparent sheet 55 increases and the effectof the openings 118 decreases.

Formed along the side wall 112 are a plurality of large openings 120.The large openings 120 reduce the fluid drag of the resin 54 as thelower planar portion 110 of the support fixture 48 is being raised orlowered in the resin 54. During fabrication of a three dimensionalarticle of manufacture 72 the large openings 120 become a greater factorthan the smaller openings 118 in reducing fluid drag when a sufficientportion of the three dimensional article of manufacture 72 is formed.The large openings 120 also provide the function of allowing residualresin 54 to drain from the support fixture 48 when the lower planarsupport portion 110 is lifted out of the resin 54 in resin vessel 20.

The large openings 120 reduce a fluid pressure difference between theresin 54 inside the side wall 112 of the support fixture 48 and outsidethe side wall 112 as the lower planar portion is being raised andlowered within the resin 54. As the lower planar portion 110 is beinglowered into the resin 54, the large openings 120 allow resin to flowinto the space above the lower planar portion 112. As the lower planarportion 110 is being raised, the large openings allow the resin to flowout of the space above the lower planar portion 112.

According to the illustrated embodiment the large openings 120 aredistributed to surround the dense array of small openings 118. The largeopenings are at least partially formed into the side wall 112. In someembodiments, individual large openings 120 span the side wall 112 and anedge of the lower support portion 110. In one embodiment a large opening120 has a cross sectional area equal to at least a plurality of thecross sectional area of one small opening 118. In another embodiment thelarge opening 120 has a cross sectional area equal to at least fivetimes the cross sectional area of one small opening 118. In anotherembodiment the large opening 120 has a cross sectional area equal to atleast ten times the cross sectional area of one small opening 118.

The side wall 112 is preferably angled relative to vertical axis Z toenable a nested stacking of the support fixtures 48. This enables astack of support fixtures 48 to be loaded into a magazine for automatedloading into a printing system 2. In one embodiment the angle of theside wall 112 relative to the vertical axis Z is in a range of 10 to 50degrees. In another embodiment the angle of the side wall 112 relativeto the vertical axis Z is in a range of 20 to 40 degrees. In yet anotherembodiment the angle of the side wall 112 relative to the vertical axisZ is in a range of 25 to 35 degrees. In a further embodiment the angleof the side wall 112 relative to the vertical axis Z is about 30degrees. There is a tradeoff in the angle. As the angle increases, arequired area of the support fixture 48 and resin vessel 20 increasesfor a given area of a build plane 68. Thus, a minimal angle may seemoptimized. However as the angle decreases, vertical stacking efficiencyof the support fixtures 48 decreases. Therefore an angle of about 30degrees from vertical is roughly an optimal tradeoff for verticalstacking efficiency versus size.

The portions 108X of the upper portion 108 that extend along the X axisinclude a plurality of bent tabs 122 that extend above an upper planarsurface 124 of the portions 108X. The bent tabs 122 are for engaging alower planar surface 126 of the portions 108X to provide a controlledvertical spacing between stacked support fixtures 48. In theillustrative embodiment an individual bent tab 122 is bent into aU-shape whereby an end of the tab 122 faces inwardly.

FIG. 6 is a flowchart representing a manufacturing method 130 for usingprinting system 2 to fabricate a three dimensional article ofmanufacture 72. Some individual steps of method 130 will also bedescribed and/or illustrated with respect to subsequent figures in addeddetail. Also, some of the earlier figures pertain to method 130. Most orall of the steps of method 130 can be under control of the controller80. For steps 132, 136, and 146 any or all of these can be performedeither manually or with a robotic arm under control of the controller80. Remaining steps 134, 138-144, and 148 can be controlled by thecontroller 80.

According to step 132, the resin vessel 20 is loaded onto support plate10. According to step 134, the interface mechanism 60 is activated tosecure the resin vessel 20 to the support plate 10 and to position theresin fluid outlet 30 and the fluid level sensor 32 over the resinvessel 20. According to step 136, the support fixture 48 is loaded ontothe fixture receiving arms 46. In some embodiments step 136 is performedbefore step 134 and/or before step 132.

According to step 138, the resin supply 56 is activated whereby theresin supply 56 supplies resin to the resin vessel 20. According to thisstep the controller 80 utilizes the fluid level sensor 32 to monitor afluid level of the resin 54 in the resin vessel 20. The controller 80activates the resin supply 56 to pump resin 54 through the supply path58 and out the resin fluid outlet 30 until a proper level of resin 54 ispresent in resin vessel 20. During subsequent steps, the controller 80can continue to monitor information from the fluid level sensor 32 andoperate the resin supply 56 to maintain a proper level of resin in theresin vessel 20.

According to step 140, the motor system 44 operates the lead screw 42 totranslate the carriage 40 whereby the lower surface 116 of supportfixture 46 is positioned at an operating distance from the transparentsheet 55. According to step 142, the light engine 50 is activated toselectively polymerize a layer of the resin onto the lower surface 116.Steps 140 and 142 are repeated until the entire three dimensionalarticle of manufacture 72 is formed. As a note, when step 140 isrepeated, it is the lower face 70 of the three dimensional article ofmanufacture 72 that is positioned at the operating distance from thetransparent sheet 55.

According to step 144, the motor system 44 is operated to raise thethree dimensional article of manufacture 72 out of the resin 54.According to step 146 the support fixture 48 is unloaded from thereceiving arms 46. According to step 148, the interface mechanism 60 isoperated to move the resin fluid outlet 30 and the fluid level sensor 32from above the resin vessel 20. Also according to step 148 the resinvessel 20 is unlatched so that it can be removed from the support plate10.

As a note various alternative embodiments are possible. For example,step 148 can be skipped and the process can proceed to step 136 wherebyanother support fixture 48 is loaded for forming another threedimensional article of manufacture 72 with the same resin vessel 20.Thus, the depicted method 130 is illustrative and lends itself tocertain variations.

FIGS. 7A-D are isometric views depicting loading and securing the resinvessel 20 and the fluid spill containment vessel 34 to the support plate10. FIG. 7A depicts step 132 of FIG. 6. The resin vessel 20 has beenloaded onto the support plate 10. A lower portion of resin vessel 20 hasbeen received into the recess 101 (see also FIG. 4). Engagement of theperipheral edge 86 and the inwardly facing wall 102 has provided lateral(X and Y) alignment of the resin vessel 20 with respect to the supportplate 10.

Also shown in FIG. 7A is a resin handling module 150 that supports boththe resin fluid outlet 30 and the fluid level sensor 32 with arms 154.The resin handling module 150 is configured to rotate about an axisparallel to lateral axis Y. In FIG. 7A the resin handling module 150 isshown in a non-operating position whereby the resin fluid outlet 30 andthe fluid level sensor 32 are not in position over the resin vessel 20.Latches 152 are also shown in a non-engaged position.

FIG. 7B depicts step 134 of FIG. 6. Between FIGS. 7A and 7B the resinhandling module 150 has been rotated about an axis parallel to lateralaxis Y from a non-operating position (FIG. 7A) to an operating position(FIG. 7B). In the operating position the resin fluid outlet 30 and thefluid level sensor 32 are both positioned over the resin vessel 20. Alsothe latches 152 are engaged with latch features 92 at opposing ends ofthe resin vessel. The latches 152 exert a downward (−Z) vertical forceon the latch features 92 to increase a tension in the transparent sheet55.

The resin handing module 150 includes two arms 154 that are linkedtogether whereby they rotate together in unison between thenon-operating position and the operating position of the resin handlingmodule 150. The interface mechanism 60 that actuates the resin handlingmodule 150 and the latches 152 is configured to simultaneously actuatethem to move them back and forth between a non-operating state(non-operating position of resin handling module 150 and latches 152 notengaged) to an operating state (operating position of resin handlingmodule 150 and latches 152 engaged).

In the illustrative embodiment, the interface mechanism 60 includespneumatic actuators 156. FIG. 7C depicts a more complete view of thepneumatic actuators 156 (shown without air “plumbing”). There is apneumatic actuator 156 coupled to each latch 152 and a pneumaticactuator 156 coupled to the resin handling module 150. The air pressureapplied to the pneumatic actuators 156 enables motion of the resinhandling module 150 and latches 152 to be simultaneous.

The resin vessel 20 is unloaded in reverse order of being loaded. Thisincludes (1) changing the interface mechanism 60 from an operating to anon-operating state—going from FIG. 7B to FIG. 7A, and then (2)unloading the resin vessel 20 from the support plate 10.

FIGS. 7C and 7D depict the fluid spill containment vessel 34 beingslidingly mounted to the lower side 36 of the support plate 10. Thefluid spill containment vessel 34 includes a transparent window 158 forallowing light to pass from the light engine 50 to the resin vessel 20.The fluid spill containment vessel 34 has a generally tapering profilefrom a distal end 160 to a proximal end 162. The tapering profileprovides an internal slope whereby resin can drain away from thetransparent window 158 and into a trough 164. This minimizes a tendencyfor a light path from the light engine 50 to the build plane 68 to beoccluded by spilled resin that has accumulated in the fluid spillcontainment vessel 34.

The fluid spill containment vessel 34 has a pair of opposing upper lips166 that extend outwardly along the lateral Y axis. Mounted to the lowerside 36 of support plate 10 are two rails 168 that are aligned withlateral axis X and spaced apart with respect to lateral axis Y. Thefluid spill containment vessel 34 is mounted to the support plate 10 byslidingly engaging the rails 168 with the upper lips 166 along thelateral axis Y.

FIGS. 7C and 7D depict disengaged and engaged positions respectively ofthe fluid spill containment vessel 34 with respect to the support plate10. In the engaged state, the resin vessel central opening 28, thesupport plate central opening 18, and the fluid spill containment vessel34 transparent window 158 are all aligned whereby the light engine 50can project pixelated light up through them and to the build plane 68.

FIG. 8A is cross sectional view depicting interaction of componentsinvolved in tensioning the transparent sheet 55 during steps 132 and 134of FIG. 6. When the resin vessel 20 is loaded onto the support plate 10,the raised ridge 104 engages the transparent sheet 55. When the latches152 engage the latch features 92, they exert a combined downward latchforce F_(L) upon the resin vessel. This has the effect of tensioning thetransparent sheet 55. The tension in the transparent sheet 55 can becontrolled by controlling the latch force F_(L).

FIG. 8B depicts the forces involved: T=Tension in Transparent Sheet 55,F_(H)=Horizontal Force Exerted on Transparent Sheet by Vessel Body 82,f=horizontal frictional force exerted on transparent sheet 55 by raisedridge 104, F_(V)=vertical force exerted on transparent sheet 55 byVessel Body 82, and F_(R)=Vertical Force Exerted by Raised Ridge 104 onTransparent Sheet 55. Now, F_(V)=W_(V)+F_(L), where W_(V) is the weightof the resin vessel 20 and F_(L) is the downward force of both latches.These forces are known.

Summing the forces in X: T+f=F_(H). Summing the forces in Y:F_(V)=F_(R). From geometry the tangent of θ equals F_(V) divided byF_(H). From the above relationships, and from computing the frictionalforce f based a coefficient of friction and F_(R), the tension T can beapproximated in terms of known variables. This diagram is a simplifiedapproximation of the actual system because it is in two dimensions andthe actual system would consider the sheet in three dimensions. If theangle θ is small, then the tension T can be quite large relative to thevertical forces applied. There may be a need to increase the verticalforce over time to compensate for an increase in angle θ if thetransparent sheet 55 stretches. The configuration of FIG. 8A has anadvantage that the latch force F_(L) can be programmably controlled bythe controller 80 controlling the air pressure applied to pneumaticactuators 156. Thus, the tension T can be indirectly programmablycontrolled by the controller 80.

FIG. 8C illustrates an alternative embodiment in which the resin vessel20 “bottoms out” on the support plate 10. With this embodiment, thetension T in the transparent sheet 55 is governed by a vertical positionof the vessel body 82 in relation to the raised ridge 104. In thisembodiment, any compression set in the transparent sheet 55 will reducethe tension T. While this embodiment is viable, it would be lessdesirable than the embodiment of FIG. 8A if the transparent sheet 55stretches over time and/or if dimensional tolerances are not preciselycontrolled.

FIG. 9 depicts a mechanical interaction between the portion 108Y of thesupport fixture 48 and receiving arm 46 as the support fixture is loadedaccording to step 136 of FIG. 6. The receiving arm 46 includesupstanding pin 170 that is received by datum feature 114 for providinglateral alignment of the support fixture 48. Between both support armsthe lateral alignment provided includes X, Y, and rotation about theaxis Z. The portion 108Y is formed from a magnetic material andreceiving arm contains a magnet. The magnetic interaction and mechanicalinteraction along the vertical axis Z between portions 108Y and thereceiving arms provide support along the vertical axis Z and againstrotation about the horizontal axes.

FIG. 10 is a top view of an embodiment of three dimensional printingsystem 2 with the resin vessel 20 and the support fixture 48 installed.The vertical support 4 has a front side 6 and a back side 8. Extendingfrom the front side 6 is the support plate 10. The support plate 10extends along lateral axis X from a proximal end 12 (proximate to thefront side 6) to a distal end 14.

Resin vessel 20 is disposed above a portion of the upper surface 98 ofsupport plate 10 (held above a recessed portion 100 of the upper surfaceby the force of the raised ridge 104 upon the transparent sheet 55). Theresin vessel 20 has a rear portion 22 that is laterally proximate to theproximal end 12 of the support plate. The resin vessel 20 has a frontportion 24 that is laterally proximate to the distal end 14 of thesupport plate. The resin vessel 20 has a pair of opposed latch features92 including left and right latch features 92 at opposed ends withrespect to the lateral axis Y. Corresponding to the left and right latchfeatures 92 are left and right latches 152.

The interface mechanism 60 (depicted in block diagram form in FIG. 2A)is activated whereby the resin handling module 150 and latches 152 arein an operating state. In the operating state the resin handling module150 is in an operating position whereby the resin fluid outlet 30 andthe fluid level sensor 32 are positioned over the resin vessel 20 andthe latches 152 are engaged with the latch features 92 of resin vessel20. The resin fluid outlet 30 and the fluid level sensor 32 are disposedover the rear portion 22 of the resin vessel 20. The resin fluid outlet30 and the fluid level sensor 32 are also spaced apart and on eitherside of the vertical support 4 with respect to the lateral axis Y andeach are supported by an arm 154 of the resin handing module 150.

Extending from the back side 8 of vertical support 4 is carriage 40.

Extending forwardly (+X) along lateral axis X from carriage 40 are thereceiving arms 46. The receiving arms 46 are spaced apart along thelateral axis Y to an extent that the arms 154 are between the receivingarms 46. Installed between receiving arms 46 is the support fixture 48that spans a space between the receiving arms 46 along the lateral axisY.

The specific embodiments and applications thereof described above arefor illustrative purposes only and do not preclude modifications andvariations encompassed by the scope of the following claims.

What is claimed:
 1. A three dimensional printing system comprising: amain vertical support; a support plate coupled to the main verticalsupport including an upper surface, a recessed surface below the uppersurface, an inwardly facing wall connecting the upper surface to therecessed surface, and a raised ridge extending upwardly from therecessed surface, a recess is defined above the recessed surface betweenthe inwardly facing wall and the raised ridge, a first central openingpassing through the support plate bounded by the raised ridge; aloadable resin vessel including: a vessel body having an inner edgesurrounding a second central opening and defining an outer peripheraledge of the loadable resin vessel; and a transparent sheet that closesthe second central opening to define a lower bound for a body of resinto be contained in the resin vessel; the outer peripheral edge of theloadable resin vessel engages the inward facing wall to laterally alignthe loadable resin vessel to the support plate when the loadable resinvessel is loaded onto the support plate as a lower portion of theloadable resin vessel is received into the recess and engagement of theouter peripheral edge with the inward facing wall further aligns thesecond central opening surrounded by the inner edge of the resin vesselto the first central opening surrounded by the raised ridge of thesupport plate, the raised ridge engages a lower surface of thetransparent sheet to tension the transparent sheet.
 2. The threedimensional printing system of claim 1 wherein the raised ridge has aninwardly facing surface that bounds the first central opening.
 3. Thethree dimensional printing system of claim 1 wherein the vessel bodyincludes a pair of latch surfaces and further comprising a pair oflatches configured to engage the pair of latch surfaces to verticallysecure the loadable resin vessel relative to the support plate.
 4. Thethree dimensional printing system of claim 3 wherein the latches exert adownward force upon the latch surfaces.
 5. The three dimensionalprinting system of claim 4, wherein the engagement of the raised ridgeand the transparent sheet prevents the vessel body from bottoming outagainst the recessed surface whereby the downward force of the latcheson the latch surfaces increases the tension in the transparent sheet. 6.The three dimensional printing system of claim 5 further comprising acontroller configured to control the downward force of the latches onthe latch surfaces to control the tension in the transparent sheet.
 7. Athree dimensional printing system comprising: a main vertical support; aloadable resin vessel including: a vessel body having an inner edgesurrounding a second central opening, an outer peripheral edge of theloadable resin vessel, and a latch surface; and a transparent sheet thatcloses the second central opening to define a lower bound for a body ofresin to be contained in the resin vessel; a support plate coupled tothe main vertical support including an upper surface, a recessed surfacebelow the upper surface, an inward facing wall connecting the uppersurface to the recessed surface, and a raised ridge extending upwardlyfrom the recessed surface, a recess is defined above the recessedsurface between the inward facing wall and the raised ridge, a firstcentral opening passing through the support plate bounded by the raisedridge, the inward facing wall engaging the outer peripheral edge of theloadable resin vessel to laterally align the loadable resin vessel tothe support plate when a portion of the loadable resin vessel is loadedinto the recess which aligns the second central opening to the firstcentral opening and aligns the raised ridge within the second centralopening; a latch for engaging the latch surface of the vessel body tosecure the vessel body to the support plate.